support 'apos' entity in HTML de-entitize, and in XML

python 3 doesn't have has_key (I tested in my CLI repl - python 2)

updates the README

adds the 'old_school' option, which is defaulted to 'true'. Setting i…

…t to 'false' will use '%20' instead of '+'

Fixes colinta#25

st2 and 3 support

fixes import

utf8 encoding

fixes for ST3 - thanks @jakemcgraw

Insert snarky comment here.

support for ST2 and ST3